The present invention relates to an automatic termination, or power cut off device, and alarm structure for motors used in multi-purpose vacuum cleaners, and more particularly, to a bifunctional vacuum cleaner suitable for sucking dust and other solid matter and also sucking liquid which includes a micro switch and a buzzer alarm, wherein the cutting off of power supply for the motor is chiefly achieved by a spherical float installed in the filter cage assembly below the sucking orifice of the motor. This float is connected with a string which passes through a fixed point and reverses direction to be connected to the spring leaf of a micro switch. When the tank is filled of liquid to a level that will raise said float to a certain height, said float will block the sucking orifice and pull the string attached to the spring leaf of the micro switch to break the power supply for motor. At this time, power supply for motor is stopped and a buzzer is connected to give out an alarm. At a result, bilateral control of water flow and high safety and longevity are achieved.
Heretofore, conventional multi-purpose vaccum cleaners use a single arrangement of a rising float to block the sucking orifice of the motor directly. As a result, the following defects will be found: (1) Incomplete blocking results and overflow occurs easily: the production technique for making the float and sucking orifice is not precise enough, and the sphericity is also not enough, complete blocking cannot be achieved and overflowing will result. (2) The motor has short working life and becomes short circuited easily: blocking of the orifice is incomplete, water will be sucked into the motor and penetrate into its circuit to cause a short working life and short circuit. (3) Idle run of the motor will cause burn-out easily and is a waste of energy: when the float rises up to block the sucking orifice, the motor is still rotating, it will be burned out easily and also cause an increase in power consumption.
Since there are so many deffects commonly existing in the known type of multi-purpose vacuum cleaner, a two-sectional control for water flow and automatic power cut off for the motor is designed which provides an alarm by means of a buzzer to achieve operation with a high degree of safety.